View the Current Issue

Article

  • The EMBO Journal (2009) 28, 3400 - 3412
  • doi:10.1038/emboj.2009.265

Published online: 1 October 2009

Failed gene conversion leads to extensive end processing and chromosomal rearrangements in fission yeast

Helen Tinline-Purvis1, Andrew P Savory1, Jason K Cullen1, Anoushka Davé1, Jennifer Moss1, Wendy L Bridge1, Samuel Marguerat2, Jürg Bähler2, Jiannis Ragoussis3, Richard Mott3, Carol A Walker1 and Timothy C Humphrey1

  1. CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, Oxfordshire, UK
  2. Department of Genetics, Evolution and Environment and UCL Cancer Institute, University College London, London, UK
  3. The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, Oxfordshire, UK

Correspondence to:

Timothy C Humphrey, Gray Institute for Radiation Oncology and Biology, University of Oxford, Old Road Campus Research Building, Oxford, Oxfordshire OX3 7DQ, UK. Tel.: +44 1865 617327; Fax: +44 1865 617318; E-mail: timothy.humphrey@rob.ox.ac.uk

Received 27 October 2008; Accepted 17 August 2009

Loss of heterozygosity (LOH), a causal event in cancer and human genetic diseases, frequently encompasses multiple genetic loci and whole chromosome arms. However, the mechanisms by which such extensive LOH arises, and how it is suppressed in normal cells is poorly understood. We have developed a genetic system to investigate the mechanisms of DNA double-strand break (DSB)-induced extensive LOH, and its suppression, using a non-essential minichromosome, Ch16, in fission yeast. We find extensive LOH to arise from a new break-induced mechanism of isochromosome formation. Our data support a model in which Rqh1 and Exo1-dependent end processing from an unrepaired DSB leads to removal of the broken chromosome arm and to break-induced replication of the intact arm from the centromere, a considerable distance from the initial lesion. This process also promotes genome-wide copy number variation. A genetic screen revealed Rhp51, Rhp55, Rhp57 and the MRN complex to suppress both isochromosome formation and chromosome loss, in accordance with these events resulting from extensive end processing associated with failed homologous recombination repair.

  • Keywords:

    • break-induced replication,
    • copy number variation,
    • DSB,
    • homologous recombination,
    • isochromosome